Field [fieldName] is expected to be type: java.util.List

[gadaldo]

I got this exception message when running it on my json string from a TableRow object.
the record is null and the schema type is:

 {
            "name": "customDimensions",
            "type": {
                "type": "array",
                "items": {
                    "type": "record",
                    "namespace": "root",
                    "name": "CustomDimensions",
                    "fields": [
                        {
                            "name": "index",
                            "type": [
                                "long",
                                "null"
                            ]
                        },
                        {
                            "name": "value",
                            "type": [
                                "string",
                                "null"
                            ]
                        }
                    ]
                }
            }
        },
...

The problem is that when I try the export of a Bigquery table with that schema, even if the record is null it works fine and gives me empty array, when I try this in a dataflow, writing the TableRow object in a GenericRecord using this great utility, then it fails.
I think Google internally does the transformation in Proto (as documented here) first and then in Avro so in these steps it probably checks if the value List is null then serialize empty array. I personally applied this check in:
Object read(Schema.Field field, Schema schema, Object value, Deque<String> path, boolean silently)
when case: ARRAY.

Thanks for help anyway.

[adamdubiel]

@pszymczyk can you take a look at this?